The long-term objective of this research is to understand how the brain translates sensory information into the commands for movements. The oculomotor system is an excellent model for study because of its simple peripheral mechanics and musculature and the ease with which eye movemcentnts can be accurately recorded. Because of these advantages, the component neuron types, their discharge patterns, and many of the connections of various oculomotor subsystems are well understood. Perhaps the most-studied type of eye movement is the quick, scanning eye movement called saccades. The goal of our research is to continue this detailed description, in order to provide the basis for determining how the neural components actually produce saccades. The ultimate aim is to provide an example of a thoroughly understood motor system that can serve as a foundation for the study of higher-order neural processes such as motor learning and attention. Although most of the component neurons of the saccaile generator have been studied extensively, there are a few missing pieces. It has become apparent that another region of the brain, the midline cerebellum, is essential to produce accurate saccades but little is known about how this is accomplished. We will continue our study of how the saccade related cerebellum contributes to saccade production by studying its output from the caudal fastigial nucleus (cFN) to the saccade generator. We will study the anatomical connections between the cerebellar cortex and the cFN and brainstem and between the cFN and the brainstem saccade generator to assess how the signals may interact in which portions of the brainstemlcerebellar saccade generator. We will examine cFN discharge during visually perturbed saccades to see if the discharge is appropriate to mediate on-line corrections. We will also study the affects of cFN reversible inactivation on visually and electrically evoked saccades. This analysis will specifically test our hypotheses that saccades are largely ballistic and that the cerebellar input serves to fine-tune the motor command. Because accurate eye movements are essential for clear vision and because oculomotor commands derive directly from visual input, these studies will contribute to our understanding of normal visual mechanisms. In addition, although the cerebellum is known to be involved in motor co-ordination, its exact function is unclear. Because of the extensive understanding of saccade production, our studies may begin to reveal exactly how the cerebellum contributes to motor co-ordination.